The test is only as good as the swab you collect. These are my recommendations: To get a good test yourself, first swab your throat back and forth then put the swab in the right nostril, as far back as comfortable and rotate in circles 2 times as you pull the swab out and then repeat on the left.
New do-it-yourself home test is a new antigen tests check for the parts of the virus and misses about 9-10% of true infections. This is the new ELLUME test. You do the entire testing and can soon order on-line or pick up at pharmacy. The cost will be about $30. It may or may not be covered by your insurance and if it is, you need to submit. Probably more options like this to come soon.
PCR tests are the most accurate where they test for the entire virus genome. You do the swab but lab runs the test. If the test is done correctly, they miss about 1% of true infections. Turnaround time is 3 to 4 days. This is a table of what is available order on-line PCR tests, no doctor RX needed. The cost is $100 to 120 depending on the test. Turn around time from ordering the test to result is 72-96 hrs.
Check with yours